Various separating agents having various specific structures adapted to the compounds to be separated are known as separating agents for chromatography. The following, for example, are known for these specific structures: crown ether-like cyclic structures, binaphthyl structures, phenyl ester structures, and phenyl carbamate structures.
Within the sphere of separating agents for chromatography that contain a crown ether-like cyclic structure and a binaphthyl structure, a separating agent for optical isomers is known in which a binaphthyl derivative having a crown ether-like cyclic structure bridging across the individual naphthyl rings in the binaphthyl is adsorbed on a carrier (refer, for example, to Patent Document 1). This separating agent for optical isomers is suitable for the optical resolution of compounds that have an amino group, e.g., amino acids.
In addition, as separating agents for chromatography in which the aforementioned binaphthyl derivative is supported by chemical bonding to a carrier, separating agents for chromatography in which the binaphthyl structure or the crown ether-like structure of a binaphthyl derivative with formula (i) or (ii) below is bonded by chemical bonding to the surface of a carrier, for example, are known (refer, for example, to Nonpatent Documents 1 and 2 and Patent Document 2). The separating agent for chromatography containing the binaphthyl derivative with formula (i) is known to have the optical resolving power with respect to amino acids, while the separating agent for chromatography containing the binaphthyl derivative with formula (ii) is known to lack the optical resolving power with respect to amino acids. Furthermore, with regard to the separating agent for chromatography that contains the binaphthyl derivative with formula (i), art is also known in which the residual silanol groups in the silica gel used as the carrier are protected by treatment using n-octyltriethoxysilane (for example, Nonpatent Document 2), and the optical resolving power with respect to α-amino acids, amines, and amino alcohols is known to be improved by this treatment.

The binaphthyl derivative with formula (i) has promise as a separating agent effective for the optical resolution of amino acids and, while it can be synthesized using commercially available products as the starting materials, the synthesis route is lengthy and there remains room for investigation from a productivity perspective.